This invention is in the field of lapping, grinding and related machine tools that produce dust particles, and particularly to lapping, grinding, polishing and related machines used with gold jewelry and that produce gold dust debris, and dust collectors for such machines.
In the jewelry making art there are many variations of high speed rotary grinding, lapping, polishing and related machines that produce dust debris of gold, silver and other precious metal particulate removed from the articles being machined. Associated with these machines are various dust collectors which utilize an air flow to direct the dust away from the machines with the metallic particulate captured downstream in filters. For convenience in this application, the term lapping machine and lap wheel will represent all these machines, since the new dust collectors disclosed herein can be used with any of these machines even though it is intended primarily for use with gold jewelry lapping machines. Such lapping machines discharge a substantial quantity of gold dust into a debris area adjacent the spinning lap wheel and from there into the close vicinity of the operators of such machines. Usually a dust collection apparatus is associated with or incorporated into the lapping machine for the purpose of collecting this gold dust.
Two main concerns about the gold dust are: (a) that it may be a dangerous pollutant to persons, animals or plant life in the vicinity, and (b) that the gold in this dust often has a considerable value that may be lost to the owners of such machinery. Also, the presence of the gold is an enticement to the operators of this machinery or to others to steal it, because of its significant value and because it is lying on the walls of the equipment where the dust has landed and can be simply wiped off with a rag or sponge. Gold extracted from this dust is readily saleable for approximately $350.00 a pound or whatever is the current price being variable with the relevant market.
Thus, for the reasons of danger to persons, animals and to the environment by this dust and for the lost value of uncollected gold, gold dust collection apparatus has been developed to reduce both of these problems.
Prior art dust collecting apparatus includes hoods and shrouds which either fully surround the work area where the dust is generated or only partially surround the area when open access to the area by an operator is required. Some dust collecting machines are as simple as a shroud or hood against which the dust strikes and falls down onto the floor of the dust collector or onto the floor of a room. Most dust collectors have suction devices attached to the shroud for drawing the dust and particles therein out of the debris area and into a collection container which usually has a filter. Such filters are periodically cleaned of the gold in a variety of routine ways.
A problem with typical gold dust collection machines is that a significant amount of gold dust is deposited on the wall surfaces and screen surfaces of the shroud or is deposited on internal walls of the conduits where the dust flows. Some gold dust is thus not readily collectable, and the visible or available gold dust becomes attractive to workers who can simply wipe it off the walls of the apparatus and consolidate it into manageable masses for subsequent sale. In a large jewelry-making factory the amount of gold dust lost to the factory owners or lost into the environment can be very significant.
One prior patent, U.S. Pat. No. 1,393,892 to Luden, for example, has a dust collector formed of inner and outer concentric walls generally surrounding the gold dust debris area. Some gold dust is captured by a liner along the inside of the inner wall; however, such a liner and collected gold can be easily stolen, and furthermore, this system does not remove the dust to a place remote from the work area.
Another prior art patent, U.S. Pat. No. 965,223 to Plant, discloses a dust gathering device which partially surrounds the abrading machine""s work area. The portion of this machine has a few openings in the inner wall, with the majority of this inner wall being solid material on which gold dust would become deposited if this machine were used for machining of gold jewelry. Gold could be easily wiped from these exposed surfaces, and this represents the typical kind of prior art problem that the present invention seeks to avoid.
A third prior art patent, Russian No. SU 1055-633-A to Kozlov, discloses a grinding tool on a horizontal shaft. Dust is circulated within this hood and collected on a peripheral filter within a hood as opposed to being exhausted externally of the hood.
Many dust collecting apparatus are not designed for use with a rotating grinding or polishing wheels which spin and direct the dust and debris radially outward from the work surface, and thus they are not concerned with the problems of dust being directed in a great multitude of directions.
The present invention pertains primarily to high speed rotating lap wheels which spew gold dust in many directions and to associated gold dust collection apparatus.
The new invention is a gold dust collector for use with lapping, grinding, polishing or related apparatus, particularly as used with gold jewelry. Typically, such apparatus has a base with an electric motor on the base and a drive shaft extending generally upwardly. As mentioned earlier, this invention will be described with respect to a lap wheel machine, but the invention is applicable to other machines with produce metal particulate and other dust debris. Attached to this drive shaft is a lap wheel that extends perpendicularly to and spins about the drive shaft axis. The jewelry piece being lapped is held by an operator below the wheel and pressed upward against it. During such lapping, particles of gold dust are thrown and spewed downward and outward, either radially or at an angle because of the rotational motion of the wheel.
In the new invention a shroud has a back and sides that partially surround the gold dust debris area which is the space primarily below the lap wheel and slightly above it. This shroud has a front wall radially spaced from the drive shaft and a rear wall spaced radially outward from the front wall, thus defining an air passageway between front and rear walls. The front wall is highly perforated to allow a maximum flow of air through the perforations and into the passageways between said front and rear walls. In the rear wall is a first exhaust port in communication with an exhaust fan or other exhaust air flow means. Thus, an air flow is established from the gold dust debris area at least below the lap wheel, outward to the perforated front wall of the shroud, then through the apertures in this wall, into the flow passages between the front and rear walls, then through the first exhaust port and finally to a filter downstream of this exhaust port. The air flows at sufficient cubic feet per minute to entrain or carry the gold dust particulate, so that at least most of the gold particulate is entrained and carried by the air flow to the terminal collection and substantially does not strike and stick to the walls of the passageways.
The shroud is open at the front to allow easy access by an operator to the front portion of the lap wheel, where the operator presses an article to be lapped upward against the bottom of the lap wheel near the front outer peripheral area thereof. In a preferred embodiment there is an additional or second exhaust port in one of the sides of the shroud situated to capture gold dust from the initial contact of the jewelry with the front of the wheel. The first exhaust port is in the rear center of the shroud at an elevation below the lap wheel, and the second exhaust port in this embodiment is in one of said side walls at an elevation at least partially below said lap wheel, and optimally at an elevation partially below and partially above said lap wheel.
In another preferred embodiment, the front wall of the shroud is formed of a wire grid material such as fence wire. The apertures defined by the wire grid are sufficiently small to prevent an operator""s fingers from reaching through to obtain any of the gold, but otherwise are as large as possible to allow the maximum flow of air therethrough.
In a still further embodiment the rear wall of the shroud is perforated leading to a manifold rearward of the rear wall that collects and directs the gold dust to an exhaust duct. These perforations may be louvers directed generally downward into the manifold.
In a typical embodiments the electric motor rotates the lap wheel at a speed of approximately 3450 rpm which is one standard in the industry. This lap wheel has four slits extending radially inward from the outer periphery, with each slit spaced apart by 90xc2x0 from adjacent slits. When a wheel of this type with the slits is rotated at a speed of 3450 rpm, the optics of the system are such that the user can see through the slits while the wheel is spinning and see with reasonable clarity the jewelry being held by his or her hands beneath the wheel as the jewelry is being lapped.
It is an additional object of this invention for the exhaust means to provide an air flow sufficient to entrain the gold dust particles, so that these particles are carried by the air and do not drop down to the floor of the air flow passage and do not leave the air flow and strike and adhere to the walls of the air flow passage.
According to one embodiment of this invention, a gold lapping machine operable with a lap wheel includes:
(a) a base,
(b) an electric motor mounted to said base, said electric motor having a rotatable output shaft extending upward and adapted to be coupled to said lap wheel which is situated above said electric motor and rotates about the axis of said output shaft, with a gold dust debris space defined as the area surrounding said lap wheel and extending from below said lap wheel downward and surrounding at least part of said output shaft,
(c) a shroud comprising rear and opposite side parts that surround the rear and opposite sides of said gold dust debris space respectively, thus leaving the front of said gold dust debris space open and accessible, said shroud comprising a continuous front wall and a continuous rear wall spaced radially outward of said front wall, with air flow passages defined between said front and rear walls of said rear and side parts, said front walls of said side and rear parts of said shroud having a plurality of apertures which comprise a majority of the surface area thereof,
(d) a first air exhaust port in said rear wall of said rear part of said shroud at an elevation below the bottom of said lap wheel, said air flow passages in said side parts of said shroud communicating with said air flow passage in said rear part and with said first air exhaust port, and
(e) exhaust air suction means communicating with said first air exhaust port for drawing air and gold dust from said gold dust debris area.
In one embodiment of this invention the shroud front and rear walls are formed as concentric semi-circular surfaces, with the air flow chamber between them being also a concentric arc. In another embodiment of this invention the front and rear walls are formed of a plurality of flat panels which together form a generally concave enclosure.
The present invention is available in a plurality of embodiments, including: (1) a lapping machine with the new shroud for gold jewelry, (2) a similar lapping machine for articles of any material that produces dust, and (3) a shroud alone for use with any lapping machine. Of these embodiments, there are table models that sit on a table or counter and exhaust at that level, and other models that may be mounted to a bench and exhaust down to floor level. Furthermore, the shroud may comprise merely a perforated front wall and a non-perforated rear wall, or perforated front and rear walls with a rear manifold behind the rear wall to collect the outflow of air and entrained dust particulate. In one embodiment the perforated front wall of the shroud is a wire fence with apertures that occupy at least a majority of the surface area. In typical embodiments the exhaust air flow system comprises a first exhaust port generally at the rear of the shroud in combination with a second exhaust port in one side of the shroud near the front, the second port located to received directly the dust particulate spewed from contact with the front of the lap wheel. Additional embodiments are described in detail below and recited in corresponding claims.
The drawings appended hereto and described herein disclose preferred embodiments which are illustrative of the features and functions of the present invention but do not limit the scope and claims to the structures shown.